Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Apr. 23, 2024	Oct. 31, 2023	Sep. 30, 2023	Oct. 31, 2022
Equity, Class of Treasury Stock [Line Items]
Share repurchase program						$ 25,000		$ 12,000
Share repurchase programs authorized	$ 23,600		$ 23,600
Preferred stock, shares issued (in shares)	5		5				5
Dividends paid	$ 1,060	$ 941	$ 2,100	$ 1,900
Preferred Stock
Equity, Class of Treasury Stock [Line Items]
Preferred stock, shares authorized (in shares)	25		25				25
Series A preferred stock
Equity, Class of Treasury Stock [Line Items]
Preferred stock, shares authorized (in shares)	4		4				4
Series B preferred stock
Equity, Class of Treasury Stock [Line Items]
Preferred stock, shares authorized (in shares)	2		2				2
Series C preferred stock
Equity, Class of Treasury Stock [Line Items]
Preferred stock, shares authorized (in shares)	3		3				3
Class A common stock
Equity, Class of Treasury Stock [Line Items]
Common stock, shares authorized (in shares)	2,000,000		2,000,000				2,000,000
Class B-1 common stock
Equity, Class of Treasury Stock [Line Items]
Common stock, shares authorized (in shares)	499		499				622
Class B-2 common stock
Equity, Class of Treasury Stock [Line Items]
Common stock, shares authorized (in shares)	123		123
Class B-3 common stock
Equity, Class of Treasury Stock [Line Items]
Common stock, shares authorized (in shares)	61		61
Class B-4 common stock
Equity, Class of Treasury Stock [Line Items]
Common stock, shares authorized (in shares)	31		31
Class B-5 common stock
Equity, Class of Treasury Stock [Line Items]
Common stock, shares authorized (in shares)	15		15
Class C common stock
Equity, Class of Treasury Stock [Line Items]
Common stock, shares authorized (in shares)	1,100		1,100				1,100
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Quarterly cash dividend (in dollars per share)					$ 0.52